Electron transfer from laser excited rydberg atoms to molecules. Absolute rate constants at low and intermediate principal quantum numbers

Abstract

Using mass spectrometric detection of positive and negative ions, we have investigated ionizing reactions of Ne(ns,nd) Rydberg atoms, efficiently excited by resonant two-photon excitation of metastable Ne(3s3P2) atoms, with electron attaching moleculesBC (BC=SF6, CCl4, CS2, O2) at thermal collision energies. Absolute rate constants have been determined in the range of low and intermediate principal quantum numbersn(5≦n≲30) by utilizing the photoionization signal caused by room temperature black-body radiation and the loss of Ne(3s3P2) atoms, associated with the laser excitation. Substantially differentn-dependences of the electron transfer cross section have been found for the larger molecules (BC = SF6, CCl4) and the smaller molecules (BC = CS2, O2). Simple model calculations have been performed to gain new insight into the dynamics of the electron transfer process; forBC = SF6, our results at lown(5 ≦n ≦ 10) suggest that internal energy conversion in the Coulombic complex Ne+ — SF 6 − is important for the formation of the detected ions.